common name: banded net-winged beetle
scientific name: Calopteron discrepans (Newman) (Insecta: Coleoptera: Lycidae)
The banded net-winged beetle, Calopteron discrepans (Newman), is a colorful black and orange net-winged beetle commonly found resting on vegetation in moist woods throughout much of the eastern United States.
Found in the eastern United States from New England south to Florida and west to Oklahoma and Kansas.
Adults: The adults range in length from approximately 10 to 15 mm. Males are smaller than females. The elytra have the elevated lengthwise ridges and cross ridges characteristic of most lycids and are orange with a median and a terminal black band.
Figure 1. Calopteron discrepans (Newman) adults mating. The smaller male is on top. Photograph by D.W. Hall, University of Florida.
The banding patterns of C. discrepans and the closely-related Calopteron reticulatum (Fabricius) are very similar in appearance. In C. discrepans, the sutural extension of the median black band is expanded basally and is widest at the scutellum. Also, the metasternum and second antennal joint are totally black in C. discrepans whereas the metasternum of C. reticulatum is more or less rufous antero-medially, and the second antennal segment is fulvous or brown (Green 1952, Dillon and Dillon 1961).
A third sympatric species, Calopteron terminale (Say) usually lacks the median black band on the elytra, and the elytra when viewed from the side are wavy with a depression anterior to the apical band. If a median band is present in C. terminale, it is not produced along the suture toward the bases of the elytra. Because of their similarity in appearance and variability of the banding patterns, the Calopteron species have often been misidentified.
Larvae: Larvae are black with burnt-orange patches.
Figure 2. Calopteron discrepans (Newman) distended prepupal larva (dorsal view). Photograph by D.W. Hall, University of Florida.
Figure 3. Calopteron discrepans (Newman) distended prepupal larva (ventral view). Photograph by D.W. Hall, University of Florida.
Figure 4. Calopteron discrepans (Newman) pupa within last instar larval pupal case. Photograph by D.W. Hall, University of Florida.
Nothing is known of the egg stage and oviposition site of Calopteron species. Calopteron larvae are reported to live in rotten logs, under loose bark or, less commonly, in soil or leaf litter. Lycid larvae are reported to be predacious by some authors (Miller 1988, Triplehorn and Johnson 2005) whereas other authors (Lawrence 1991, Marshall 2006, McCabe and Johnson 1979, Withycombe 1926) report that they feed on myxomycetes, fungi, or fermenting plant juices.
Full-grown larvae of Calopteron species aggregate prior to pupation (McCabe and Johnson 1979, Moffat 1883, Withycombe 1926).
Figure 5. Prepupation aggregation of larvae of Calopteron sp. Photograph by Lyle J. Buss, University of Florida.
These aggregations may contain hundreds of pupae packed together in shingled masses. The C. discrepans aggregation pictured below is part of a larger aggregation that contained over 600 pupae.
Figure 6. Calopteron discrepans (Newman) pupal aggregation and newly emerged adult. Photograph by D.W. Hall, University of Florida.
The colorful adults of C. reticulatum have been shown to contain pyrazines (that likely impart the repugnant scent of the beetles) and lycidic acid and other fatty acids that may render them distasteful to predators (Eisner et al. 2005), and other species of Calopteron are also likely distasteful. The integument of Calopteron larvae also displays bright, contrasting coloration, and the larvae are likely distasteful. Pupation occurs within the last instar larval exoskeleton (Young and Fischer 1972). The exoskeletons which retain the bright larval coloration probably provide not only shelter but also aposematic (warning coloration) benefit to the pupae. Aggregation of aposematic insects is generally believed to be adaptive as a defensive mechanism against predators (Riipi et al. 2001, Vulinec 1990), and that is the presumed benefit of the pre-pupation aggregation behavior of Calopteron.
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- Eisner T, Eisner M, Siegler M. 2005. Secret Weapons: Defenses of Insects, Spiders, Scorpions, and Other Many-Legged Creatures. Harvard University Press. Cambridge, Massachusetts. 384 pp.
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- McCabe TL, Johnson LM. 1979. Larva of Calopteron terminale (Say) with additional notes on adult behavior (Coleoptera: Lycidae). Journal of the New York Entomological Society 87: 283-288.
- Miller RS. 1988. Behavior of Calopteron reticulatum (F.) larvae (Coleoptera: Lycidae) Ohio Journal of Science 88: 119-120.
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- Triplehorn CA, Johnson NF. 2005. Borror and DeLong's Introduction to the Study of Insects. 7th edition. Thomson Brooks/Cole. Belmont, California. 864 pp.
- Vulinec K. 1990. Collective security: aggregation by insects as a defense, pp. 251-288. In Evans DL, Schmidt JO. [editors] Insect Defenses: Adaptive Mechanisms and Strategies of Prey and Predators. State University of New York Press. Albany, New York. 482 pp.
- Withycombe CL. 1926.The biology of lycid beetles in Trinidad. Proceedings of the Entomological Society of London. 1: 32-33.
- Young DK, Fischer RL. 1972. The Pupation of Calopteron terminale (Say) (Coleoptera: Lycidae). Coleopterists. Bulletin 26: 17-18.